183，常用控件自带的代理使用方法

#import "ViewController.h"

/**

* (1)代理的作用：监听那些不能通过addTarget监听的事件！

* 主要负责在两个对象之间，发生某一些事件时，来传递消息和数据

* (2)代理的实现步骤：

* 成为（子）控件的代理，父亲（控制器）成为儿子（文本框）代理

* 遵守协议

* 实现协议的方法

*/

@interface
ViewController () <UITextFieldDelegate>

@property (weak,
nonatomic) IBOutletUITextField *username;

@property (weak,
nonatomic) IBOutletUITextField *password;

@end

@implementation ViewController

-(void)viewDidLoad{

[superviewDidLoad];

[self.usernamebecomeFirstResponder];

self.username.delegate =self;

self.password.delegate =self;

}

- (IBAction)load:(UIButton *) button {

NSLog(@"username = %@,password = %@",self.username.text,self.password.text);

}

-(BOOL)textFieldShouldReturn:(UITextField *)textField{

if(textField ==
self.username){

[self.passwordbecomeFirstResponder];

}else{

[self load:nil];

[self.viewendEditing:YES];

}

return
YES;

}

@end